The present invention relates to an alcohol free microemulsion, containing fragrance, and more especially to transparent oil in water microemulsion concentrates which consist essentially of water, one or more hydrophobic fragrance oils and one or more surface active agents. In another aspect, the present invention relates to a method for preparing transparent microemulsion perfume compositions.
Alcohol containing fragrances are the mostly commonly used vehicle in preparing fine perfumes. Alcohol has the advantage of being a material that has a fast evaporation rate and a strong lift of the fragrance after application to the skin. There is a worldwide incentive to reduce the use of volatile organic chemical (VOC). The replacement of alcohol base product by microemulsion based product is considered as a step in this direction. The market of alcohol free fragrances constitutes a new segment of activity which has an important growth potential in the future. Since this trend is recent, all the advantages of alcohol-free fragrances have yet to be discovered. In any case, the success of this product is based on the potential to harmonize the aroma chemical with the aqueous base. This involves the proper choice of aroma chemicals to generate a different olfactory experience, but also the proper choice of surfactant and surfactant concentration, to impart transparency and skin substantivity.
There is currently a movement in the perfume industry towards elimination of alcohol in fragrances and the development of water based fragrances and perfumes. These new formulations would have the advantage of eliminating the problems caused by volatile organic chemical restrictions imposed by various countries as well as objections from environmentalist groups and persons concerned with infant safety as well as objections to alcohol in some countries based on religious grounds. Hence there have been many efforts to utilize water as a solvent for perfumes.
Water as a solvent for perfumes does have problems because it has different characteristics and properties from alcohol in terms of solubilities, drying rates, odor and the like. As a result, efforts in the past to utilize water as a base for perfumes has not been met with great success.
One approach to prepare water based perfume formulations has resulted in the development of microemulsion technology which is capable of yielding a clear to opalescent, low viscosity solution.
The concept of the microemulsion was introduced by Schulman and Montague, Ann. New York Academy of Science, 1961, Volume 92, page 366. Becher, American Chemical Society Symposium Series 448, ACS, Washington, D.C. 1991 contains two chapters covering microemulsions in foods: Chapter 1, El-Nokaly, et al. and Chapter 2, Friberg, et al. The microemulsion system typically contains relatively large amounts of oil and water along with a surfactant and co-surfactant except in the case of certain hydrophobic surfactants where no co-surfactant may be required. These systems are indicated in the prior art to form spontaneously as a result of contact between the several components.
The most characteristic difference between an emulsion and a microemulsion is the appearance of the microemulsion and the emulsion. An emulsion is turbid while the microemulsion is transparent.
Rosano, U.S. Pat. No. 4,146,499 issued on Mar. 27, 1979 discloses a method for the preparation of oil-in-water microemulsions via a four-step process: 1) a surfactant is selected which is just barely soluble in the oil phase; 2) the surfactant thus selected is dissolved in the oil to be emulsified in an amount effective to yield a fine emulsion of the emulsified oil in an aqueous phase; 3) the oil, together with its dissolved surfactant is added to the water phase and shaken or stirred; and 4) finally there is provided a second surfactant in the water phase which is somewhat more soluble in water than the first surfactant to produce a substantially clear microemulsion of oil in water. Wolf, et al. U.S. Pat. No. 4,835,002 issued on May 30, 1989 discloses microemulsions of edible oils in a matrix of water and certain alcohols which are prepared using certain edible surfactants for use in various products such as beverages. El-Nokaly, et al. U.S. Pat. No. 5,045,337 issued on Sep. 3, 1991 discloses microemulsions which are thermodynamically stable, clear and homogeneous which are made from a polar solvent, a specific polyglycerol mono, diester and a lipid. El-Nokaly, et al. discloses that these microemulsions are edible, have good flavor and can be used to disperse water soluble nutrients, vitamins, flavors and flavor precursors in oils. The polyglycerol mono diester in El-Nokaly, et al. consists of a mixture of mono and diesters of branched or unsaturated fatty acids having from 12 to 24 carbon atoms and a polyglycerol mixture consisting of 0% to 10% monoglycerol and other polyglycerols, 30% of less diglycerol, 25% to 50 triglycerol, 15 to 50% tetraglycerol. Tabibi, et al. U.S. Pat. No. 5,130,122 issued on Jul. 14, 1992 discloses oral cavity and dental products prepared by microemulsifying an adsorptive oil in an aqueous medium to produce uniform submicron sized droplets. It is disclosed by Tabibi, et al. that the disclosed therein avoid the generally unaesthetic, oily, and unpleasant taste problems of previous similar products. For certain fragrances compositions known in the art, the combustion of a solubilizer which is a high HLB surfactant with a fragrance oil does not provide an adequate range of clear product.